Method of desulphurizing rayon



Patented Oct. 16, 1934 UNITED STAT-ES v 1,977,533 METHOD OF DESULPHURIZING RAYON Gilbert I. Thurmond, West Asheville, N. 0., as signor to American Enka Corporation, Erika, N. 0., a corporation of Delaware Na Drawing. Application December 29, 1933, Serial No. 704,595

9- Claims. (Cl. 18--54) 'I'hisapplication is'a continuation in part of my copending application Serial No. 657,745,

filed February 20, 1933. 3

The present invention relates to aprocess of desulphurizing rayon and an improved solution to be employed in carrying out the process. More particularly the rayon is treated in the form of packages such as spinning cakes, bob bins, cops, perforated carriers and the like.

1 Heretofore the various solutions which have been employed, included alkaline reagents for the purpose of desulphurizing the rayon and neutralizing the acids contained therein. These alkaline reagents which have been commonly used are sodium carbonate, sodium sulphide, sodium sulphite, and other similar compounds. In so far as the adaptability of these reagents for neutralizing and desulphurizing is concerned, relatively successful results have been obtained. 20 However, it is necessary that the package of rayon be entirely free from iron compounds as these known types of desulphurizing agents will precipitate the iron in the form of insoluble salts which is very detrimental to the yarn.

It has therefore been the usual procedure to first thoroughly wash the freshly spun package for the removal of free acids and soluble salts, prior to the desulphurizing step. This washing consumed considerable time in that it was nee-'- essary for the package to be substantially entirely free from impurities.

Even'with this lengthy washing operation it has been impossible to remove all of the iron compounds. The reason for this is that a certain amount of iron exists in the spinning solution, the spinning bath, and even in the desulphurizing solution itself. Therefore in the subsequent desulphurizing treatment it was found that the ordinary alkaline reagents, which were employed precipitated a certain amount of iron, in the form of insoluble salts, in and on the yarn, resulting in what is known as an iron stain.

It is therefore highly desirable in order to eliminate the iron stain to introduce in the desulphurizing solution an agent which will maintain the iron in a soluble state, which will also have a neutralizing and desulphurizing effect on the yarn, and which will not further be reactive with the common reagents employed in conjunction therewith.

It is therefore the object of the present invention to provide an agent having the above stated necessary properties which will additionally prevent the precipitation of ironcompounds on and in the yarn.

It is a further object of the invention to incorporate sodium bicarbonate, sodium carbamate, sodium carbamide and thelike in the ordinary desulphurizing solution so that the washing step prior to the 'desulphurizing step may be eliminated.

In accordance with the present invention it has been found that the originalwashing of the packages of rayon may be dispensed with and the iron compounds will be maintained in a soluble state, if sodium bicarbonate, sodium carbamate, or sodium carbamide is incorporated in the ordinary desulphurizing solution. The desulphmizing soiution may contain any one of the above stated alkaline desulphurizing agents, such as, for instance, sodium carbonate or sodium sulphide.

After the rayon filaments have been spun or wound. into package form, the packages are brought directly into contact with the desulphurizing solutions. The alkaline reagents employed plus a reagent for preventing the precipitation of iron, such as sodium bicarbonate, act to neutralize the acids in the packages and also desulphurize. The sodium bicarbonate prevents the precipitation of iron even though a substantial amount of iron salts is present.

Any suitable method for applying the desulphurizing solution may be employed. Whereas the so-called drip method is generally em ployed for desulphurizing cake spun packages, the packages may be, if desired, immersed in the solution. Either method may be applied to bobbin spun packages or if the packages are wound on perforated carriers the solution can be caused to flow under pressure from the interior of the package outwardly or from the exterior of the package inwardly, by the use of a pressure or suction.

The proportions of the alkaline reagents and the compounds for preventing the precipitation of iron can vary with relation to the solution or to themselves depending on the conditions and the results desired. For instance, the amount of alkaline reagents such as sodium carbonate, to be added to the solution, may vary up to 5% of the solution. In the same manner the compounds for preventing the precipitation of iron may vary up to 5%. Very satisfactory results have been obtained by using an alkaline reagent existing in a range between about 0.1% and 1.5%, and sodium bicarbonate between 0.1 of 1% and 1.0% of the solution.

One example of a very efficient desulphurizing solution which has been employed, is one in which approximately .3% of the solution is sodium carbonate and .15% of this solution is sodium bicarbonate.

The spinning packages can be, if desired, first given a short water washing treatment to remove a large proportion of the acids occurring in the package. This, however, is not necessary.

After the desulphurizing step is completed, thea package can be given a thorough washing with water to remove the alkaline reagents including the compounds employed 'to-prevent the precipitation of iron, such as, sodium bicarbonate. This, however, will not" be necessary if the next operation would not in any way be impaired by the presence of a small amount of the alkaline reagents. The other salts which were initially present in the package will have been substantially completely removed by the desulphurizing solution.

Whereas the invention has beendescribed in which an improved desulphurizing solution is employed in the treatment of rayon packages, it is to be understood that the scope of the novelty is to include broadly a process and solution for maintaining the iron compounds, occurring in the packages, in a substantially completely soluble state.

Having thus described my invention, what I claim is:

1. A process for desulphurizing rayon in package form which comprises treating the package with an ordinary alkaline desulphurizing solution, to which solution has been added a reagent of the class consisting of an alkali bicarbonate, alkali carbamide, and alkali carbamate, which will maintain the iron compounds occurring in the package in a soluble state.

2. A process for desulphurizing rayon in package form which comprises treating the package with an ordinary alkaline desulphurizing solution, to which solution has been added an alkali bicarbonate, which will maintain the iron compounds occurring in the package in a soluble state. g

. 3. A process for desulphurizing rayon in package form which comprises treating the package with an ordinary alkaline desulphurizing solution, to which solution has been added an alkali carbamide, which will maintainthe iron compounds occurring in the package in a soluble state.

4. A process for desulphurizing rayon in package form which comprises treating the package with an ordinary alkaline desulphurizing solution, to which solution has been added an alkali carbamate, which will maintain the iron compounds occurring in the package in a soluble state.

5. A process according to claim 1, in which the ordinary desulphurizing solution comprises an aqueous solution of sodium carbonate and the like.

6, A process for desulphurizing rayon in package ,form which comprises treating the package with an ordinary desulphurizing solution containing sodium carbonate and the like existing in a range between approximately .1% and 1.5%,

to which solution has been added a reagent of the class consisting of sodium bicarbonate, sodium carbamide, and sodium carbamate, in a range between approximately .l% and 1%, which will maintain the iron compounds occurring in the package in a soluble state.

7. A process for desulphurizing rayon in package form which comprises treating the package with an ordinary desulphurizing solution containing sodium carbonate and the like existing in a range between approximately .1% and 1.5%, to which solution has been added sodium bicarbonate, in a range between approximately .1% and 1%, which will maintain the iron compounds occurring in the package in a soluble state.

8. A process for desulphurizing rayon in package form which comprises treating the package with an ordinary desulphurizing solution containing sodium carbonate and the like existing in a range between approximately .l% and 1.5%, to which solution has been added sodium carbamide, in a range between approximately .1% and 1%, which will maintain the iron compounds occurring in the package in a soluble state.

9. A process for desulphurizing rayon inpacks .age form which comprises treating the package with an ordinary desulphuriz'ing solution containing'sodium carbonate and the like existing in a range between approximately .l% and 1.5%. to which solution has been added sodium. carbonate, in a range between approximately .1% and 1%, which will maintain the iron compounds occurring in the package in a soluble statel,

GILBERTI. THURMOND. 

